Lipopeptides from the Banyan Endophyte, Bacillus subtilis K1: Mass Spectrometric Characterization of a Library of Fengycins

Pathak, Khyati V and Keharia, Haresh and Gupta, Kallol and Thakur, Suman S and Balaram, Padmanabhan (2012) Lipopeptides from the Banyan Endophyte, Bacillus subtilis K1: Mass Spectrometric Characterization of a Library of Fengycins. In: JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY, 23 (10). pp. 1716-1728.

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Abstract

Mass spectrometric analysis of a banyan endophyte, Bacillus subtilis K1, extract showing broad spectrum antifungal activity revealed a complex mixture of lipopeptides, iturins, surfactins, and fengycins. Fractionation by reversed-phase high performance liquid chromatography (HPLC) facilitated a detailed analysis of fengycin microheterogeneity. Matrix assisted laser desorption ionization (MALDI) and electrospray ionization (ESI) mass spectrometric studies permitted the identification of several new fengycin variants. Four major sites of heterogeneity are identified: (1) N-terminus beta-hydroxy fatty acid moiety, where chain length variation and the presence of unsaturation occur, (2) position 6 (Ala/Val/Ile/Leu), (3) position 10 (Val/Ile) within the macrocyclic ring, and (4) Gln to Glu replacement at position 8, resulting in fengycin variants that differ in mass by 1 Da. Diagnostic fragment ions provide a quick method for localizing the sites of variation in the macrocycle or the linear segment. Subsequent establishment of the sequences is achieved by MS/MS analysis of linear fengycin species produced by hydrolysis of the macrocyclic lactone. Unsaturation in the fatty acid chain and the presence of linear precursors in the B. subtilis K1 extract are also established by mass spectrometry. The anomalous distribution of intensities within isotopic multiplets is a diagnostic for Gln/Glu replacements. High resolution mass spectrometry facilitates the identification of fengycin species differing by 1 Da by localizing the variable position (Gln(8)/Glu(8)) in the fengycin variants.

Item Type:	Journal Article
Publication:	JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
Publisher:	SPRINGER
Additional Information:	Copyright for this article belongs to SPRINGER
Keywords:	Cyclic lipopeptides;Fengycin; Surfactins;Iturins;Mass spectrometry;Isotopic multiplet
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	22 Nov 2012 10:29
Last Modified:	22 Nov 2012 10:29
URI:	http://eprints.iisc.ac.in/id/eprint/45316

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